Prenatal detection and diagnosis of genetic variations and pathological conditions are useful for monitoring and maintenance of health and well-being of both mother and fetus. Non-invasive methods are lacking for obtaining and analyzing fetal cells which are typically few in number. There is a continuing need for assays to alert clinicians to abnormalities in ongoing pregnancies, such as Down Syndrome and other chromosome number disorders, diagnosis of inherited diseases, and pathologies of the fetus in pregnancies in which preeclampsia or intrauterine growth restriction will develop.